Phenol-bis-amide stabilizer combinations for polyolefins

ABSTRACT

Alkycarboxyalkylthio propionamides are effective stabilizers for polyolefine. N,N&#39;&#39;-methylene-bis( Beta -(alkylcarboxyalkylthio)propionamides) and hexahydro-1,3,5-tris( Beta (alkylcarboxyalkylthio)propionyl)-a-triazines are particularly useful stabilizers for polyethylene and polypropylene. The present alkylcarboxyalkylthio propionamides behave synergistically in combination with phenolic stabilizers derived from isocyanurates and 1,3,5-triazines.

United States Patent [191 Beears PHENOL-BIS-AMIDE STABILIZER COMBINATIONS FOR POLYOLEFINS [75] Inventor:

22 Filed: Apr. 23, 1971 21 Appl. No.; 137,066

Related US. Application Data [62] Division of Ser. No. 873,651, Nov. 3, 1969,

abandoned.

Warren L. Beears, Brecksville, Ohio [52] US. Cl 260/45.8 N, 260/45.85 S [51] Int. Cl. C08f 45/60 [58] Field of Search 260/45.8 N, 45.85 S,

260/481 R, 45.8 NT; 99/163 [56] References Cited UNITED STATES PATENTS 2,615,889 10/1952 Zerner et a1 260/248 2,792,307 5/1957 Chenicek 99/163 2,981,717 4/1961 Boultbee 260/45.85 3,165,552 1/1965 Lovett et a1. 260/561 3,206,402 9/1965 Critchley et a1. 252/47.5 3,531,483 9/1970 Gilles 260/248 3,538,092 11/1970 Dexter 260/248 Primary Examiner-Donald E. Czaja Assistant Examiner-R. A. White Att0rneyJ. Hughes Powell, Jr.

[57] ABSTRACT Alkycarboxyalkylthio propionamides are effective stabilizers for polyolefine. N,N'-methylene-bis[B-(alkylcarboxyalkylthio)propionamides] and hexahydro- 1,3 ,5-tris[ B-(alkylcarboxyalkylthio)propionyl1-atriazines are particularly useful stabilizers for polyethylene and polypropylene. The present alkylcarboxyalkylthio propionamides behave synergistically in combination with phenolic stabilizers derived from isocyanurates and 1,3,5-triazines.

6 Claims, No Drawings PHENOL-BIS-AMIDE STABILIZER COMBINATIONS FOR POLYOLEFINS This is a division of application Ser. No. 873,651, filed Nov. 3, 1969, now abandoned.

BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION Novel alkylcarboxyalkylthio propionamides containing a plurality of thio groups have now been discovered and are highly effective stabilizers for polyolefins, especially when employed in combination with a phenolic stabilizer. Methylenebis (alkylcarboxyalkylthio propionamides) and hexahydro-l ,3 ,5-tris(a1kylcarboxyalkylthio propionyl)-s-triazines are particularly useful employed in the range between about 0.01 and 5 percent by weight of the total composition. Employed in combination with phenolic stabilizers derived from isocyanurates and 1,3,5-triazines, an exceptional synergistic effect is obtained. Particularly effective stabilization of polyethylene and polypropylene is observed when mefhylerieliflalkylcaiboxyalkylthio propioria mide) or hexahydro-l,3,S-tris(alkylcarboxyalkylthio propionyl)-s-triazine is combined with a tris(3-alkyl-4- hydroxybenzyl)isocyanurate in essentially a 1:1 weight ratio.

DETAILED DESCRIPTION This invention relates to a new class of compounds effective for the stabilization of polyolefins, particularly polyethylene and polypropylene. The present compounds are alkylcarboxyalkylthio propionamides and more specifically bisor tris-alkylcarboxyalkylthio propionamides. The compounds contain a plurality of groups of the structural formula 6 g N CHCHzS(CHz)=COOR (I) .through a methylene (CH or other alkylene {CH- radical containing up to 8 carbon atoms. The remaining valency of the nitrogen atom is satisfied with a hydrogen atom. Excellent results have been obtained with bis-alkylcarboxyalkylthio propionamides having the structural formula where R is an alkyl radical containing from 12 to 25 carbon atoms. Compounds corresponding to the structural formula (II) include: N,N'-methylene-bis[[3(ndodecyl-2-carboxyethylthio) propionamide], N,N- methylene-bis[B-(n-dodecylcarboxymethylthio)propionamide N ,N -methylene-bis[ B-( n-dodecyl-2- carboxyethylthio )-a-methylpropionamide N,N methylene-bis[B-(n-dodecylcarboxymethylthio)-amethylpropionamide N ,N -methylene-bis- [hexadecyl-2-carboxyethylthio)propionamide], N,N- methylene-bis[hexadecylcarboxymethylthio)propionamide N,N '-methylene-bis[B-(octadecyl-2- carboxyethylthio )propionamide], N,N '-methylenebis[,B-(octadecyl-2-carboxyethylthio)-a- I methylpropionamide], N,N-methylene-bis[B (octadecylcarboxymethylthio )-amethylpropionamide], and the like.

Other useful tris-alkylcarboxyalkylthio compounds are those where the nitrogen atom of formula (I) is a member of a l,3,5-triazine ring. With the 1,3,5- triazine-based compounds, three groups of formula (I) can be present. Effective stabilizers are obtained, however, if only two groups of the formula (I) are present. Highly effective stabilizers derived from 1,3,5-triazine correspond to the formula Illl CH7 0 R1 (III) wherein R and R are the same as defined above. Such compounds include: hexahydro-l ,3 ,5-tris[[3-( ndodecyl-2-carboxyethylthio)propionyl]-s-triazine, hexahydrol ,3 ,5 -tris[ B-(n-dodecylcarboxymethylthio)propionyl]-s-triazine, hexahydrol ,3 ,5-tris[,B-(n-dodecyl- 2-carboxyethylthio)-a-methylpropionyl]-s-triazine, hexahydro-l ,3 ,5-tris[/3-(n-dodecylcarboxymethylthio)-amethylpropionyl]-s-triazine, hexahydrol ,3 ,5-tris [B- tetradecyl-2-carboxyethylthio)propionyl]-s-triazine, hexahydro-l ,3 ,5-tris[,B-(hexadecyl-2- carboxyethylthio )propionyH-s-triazine, hexahydrol ,3 ,5-tris[B-(octadecyl-2-carboxyethylthio) propionyl]-s-triazine, hexahydro-l ,3 ,5-tris[ B- (octadecylcarboxymethylthio)propionyl]-s-triazine, hexahydro-1,3,5-tris [B-(octadecyl-Z- carboxyethylthio)-a-methylpropionyl]-s-triazine, hexahydro-l ,3 ,5-tris[B-(0ctadecylcarboxymethylthio)-amethylpropionyl]-s-triazine, and the like.

Compounds of the formulae (II) and (III) are conveniently prepared by reacting the ester of a mercapto acid with a compound containing acrylylor methacrylyl-substitution. For example, to obtain compounds of type (II), 2 mols of the ester of the mercapto acid are reacted with 1 mol methylene bis-acrylamide. To obtain compounds of type (III), 3 mols of an ester of a mercapto acid are reacted with 1 mol of the acrylylor methacrylyl-substituted s-triazine. The reactions are generally conducted in a solvent medium with a basic catalyst. The catalyst can be an alkali or alkaline kali metal alkoxides such as sodium methoxide may 5 also be employed to catalyze the reaction. The reaction is generally conducted at an elevated temperature generally not exceeding about 70C. To avoid unduepolymerization of the acrylyl or methacrylyl groups a small amount of a conventional polymerization inhibitor can be addedto the reaction mixture. The alkylcarboxyalkylthio propionamides are readily recovered from the reaction mixture using conventional techniques. The examples willmore clearly illustrate the process for preparing the present compounds.

The amy lcarboxfiilkylthiopropionamides are useful stabilizers for olefin polymers. Although polypropylene and polyethylene are most advantageously stabilized, the present compounds are equally effective to stabilize other polyolefins derivedfrom a-olefins containing up to about 8 carbon atoms such as poly-4-methylpentenel, polybutene and the like. They are also useful to stabilize polyolefin copolymer compositions such as ethylene-propylene copolymers. Physical mixtures of olefin homopolymers and copolymers are also stabilized according to the present invention. The polyolefins may be of high density, medium density or low density. About 0.01 percent to about 5 percent by weight of the stabilizer based on the total stabilized composition is normally employed. Excellent stabilities are observed when about 0.1 percent to about 3 percent by weight of the stabilizer is used.

The alkylcarboxyalkylthio propionamides impair oxi dative deterioration as well as thermal degradation and degradation resulting from photochemical exposure which occurs during the manufacture, processing or use of the polyolefin. Such degradation generally causes a loss in the dielectric properties, discoloration, embrittlement and a decrease in other physical properties of the polymer. The present stabilizer compounds are highly effective to reduce the adverse effects caused by degradation. The polyolefinic materials sta-' bilized with the compounds of this invention are useful for thermoplastic molding and coating applications as well as having a wide variety of other applications well known to the art.

The stabilizer compounds of this invention ar? In addition to the stabilization of polyolefins the present compounds are also useful to stabilize other polymer compositions, oils, lubricants, saturated and unsaturated hydrocarbons and like materials which are subject to oxidative attack. Polystyrene, for example, or copolymers of butadiene and styrene may be stabilized with the present compounds. Also effectively stabilized are various types of lubricating oils, fatty materials such as the oils of animal and vegetable origin, gasoline, mineral oil, diesel oil, drying oils and resins.

Although the present bis arid tris-alkylcarboxyalkylthio propionamides are useful stabilizers for polyolefins when employed by themselves, particular advantage is obtained when at least one of these comnolic stabilizer compound. The phenolic stabilizers will contain one or more hindered phenol groups substituted on a 6-membered nitrogen-containing heterocyclic ring structure. Although enhanced activity is observed when the alkylcarboxyalkylthio propionamides are combined with conventional phenolic stabilizers, a very marked and unexpected increase in stabilization over these combinations is obtained when the phenolic stabilizer is one derived from an isocyanurate or 1,3,5- triazine. The heterocyclic nucleus will contain three alternating nitrogen heteroatoms, that is, in the 1,3 and 5 ring positions. When phenolic-substituted isocyanurates or 1,3,5-triazines are used in combination with the alkylcarboxyalkylthio propionamide compounds,

the stabilization achieved far surpasses that obtained with either compound alone at the same level or the sum of the individual stabilizer compounds when employed alone. A completely unexpected improvement in the stability of the olefin polymers is realized, sometimes even exceeding ten times that obtained with ei ther compound alone under the same conditions.

The phenolic substituents are preferably 4- hydroxyaryl groups containing one or two alkyl substit- 0 uents immediately adjacent (ortho) to the hydroxyl tuted compounds are particularly advantageous for the present invention.

rate or 1,3,5-triazine rings may be made through a varireadily incorporated by conventional methods into the ety Oflillkages- For p thephenolic moiety y polyolefin and generally require no special processing. They are added to the polymers by mixing on a mill or in a Banbury mixer and they may be added, alone in a suitable solvent or masterbatched with other ingredients, to a solution of the polymer. The ready solubility of these compounds in a wide variety of organic solvents facilitate their use in solution and also renders them compatible with most oils and lubricants. They can be used with other compounding ingredients such as processing oils, plasticizers, lubricants, fillers, reinforcing agents and the like. They are also compatible with other known oxidative stabilizers, color and heat stabilizers, ultraviolet absorbers and the like.

Particular advantage is realized when the alkylcarboxyalkylthio propionamides are employed in combination with hydroxyphenylalkyleneyl isocyanurates of the general formula pounds is employed in combination with another phe-v EXAMPLE I Preparation of hexahydro-l,3,5-tris-[B-(n-octadecylcarboxymethylthio)propionyl]-s-triazine.

To a reactor equipped with a stirrer and condenser was charged 12.45 grams (0.05 mol) 1,3,5- triacrylylperhydro-s-triazine and 160 mls. chloroform containing 0.1 gram 2,6-di-t-butyl-p-cresol as a polymerization inhibitor. 51.6 Grams (0.15 mol) N- octadecylthio acetate and 0.6 gram of a 35 percent solution of trimethylbenzyl ammonium hydroxide in methanol were then charged and the reaction mix-ture heated at 50C. under a nitrogen atmosphere for about 2 hours. The reaction mixture was cooled and acidified by the addition of0. 125 gram concentrated hydrochloric acid and the chloroform removed under reduced pressure at a temperature of about 75C. About 63 grams of a crude white solid was obtained upon cooling. The crude light amber hexahydro-l,3,5-tris[B-(noctadecylcarboxymethylthio)propionyl]-s-triazine was recrystallized from hexane and obtained as a white crystalline solid having a melting point of 767 8C. Elemental analysis, infrared analysis and nuclear magnetic resonance spectroscopy all confirmed the compound to be hexahydro-l ,3,5-tris[B-(noctadecylcarboxymethylthio)propionyl]-s-triazine.

EXAMPLE II Preparation of hexahydro-l ,3 ,5-tris[,B-(n-octadecyl-2- carboxyethylthio)propionyl]-s-triazine Employing a procedure similar to that described in Example I, 40 grams (0.112 mol) n-octadecyl-B- mercaptopropionate and 8.6 grams (0.0373 mol) 1,3,- -triacrylylperhydro-s-triazine were reacted in 150 mls. chloroform containing 0.1 gram 2,6-di-t-butyl-p-cresol and 1 gram of a 35 percent methanol solution of trimethylbenzyl ammonium hydroxide. About 100 percent yield of crude hexahydro-l,3,5-tris[B-(noctadecyl-2 -carboxyethylthio)propionyl]-s-triazine was obtained. Recrystallization of the crude reaction product from acetone yielded a product having a melting point of 70-71C. Elemental analysis and the infrared spectrum corres-ponded with that for hexahydrol,3,5-tris[,B-(n-octadecyl-2-carboxyethylthio )propionyl]-s-triazine.

' PART II. STABILIZATION OF POLYOLEFINS The alkylcarboxyalkylthio propionamides prepared in Examples I and II and other alkylcarboxyalkylthio propionamides similarly prepared were employed to stabilize polyolefins. Comparative Examples were run to demonstrate the superiority of the present compounds over several well known commercial stabilizers. All stabilizers were incorporated into the polyolefin by dissolving the stabilizer in acetone, suspending the polyolefin therein and then removing the acetone under vacuum. The stabilized polyolefin compositions were then hot milled. In the case of polyethylene and polypropylene the milling was conducted for 5 minutes at 290300F. The polyolefin was then sheeted off and placed in a mold shimmed to the desired thickness. Polyethylene samples were then heated in the mold at 300F. for minutes with 150 tons pressure being applied over the last 5 minutes of heating and the samples allowed to cool in the mold under pressure. Polypropylene samples were molded at 400F. and 4,000 psi for 2 minutes and then transferred to a cold press at 4,000

psi for a 2 minute cooling period. The samples were tested by hanging 1 X 2 inch strips in an air-circulating .oven and heating at a temperature of C. The samples were deemed to have failed at the first signs of crazing.

EXAMPLE III Polypropylene was stabilized with hexahydro-l,3,5- tris[B-(n-octadecylcarboxymethylthio)propionyH-striazine and a well known commercial thio compound by themselves, and in combination with several phenolic stabilizers. The amounts of proplonyll-s-triazine (0.1). (0.25).

the stabilizers employed and the results obtained there-- with are set forth in the table. It is evident from the table that the hexahydro-l,3,5-tris[B-(noctadecylcarboxymethylthio)propionyH-s-triazine is effective to prevent oxidative degradation of polypropylene. It is also shown that when the alkylcarboxyalkylthio propionamide compound is employed in combination with a phenolic isocyanurate compound, tris(3,- 5-di-t-butyl-4-hydroxybenzyl)isocyanurate, synergistic activity is obtained. This synergism is even more remarkable since it is much greater than the synergistic effect obtained when well known thio compounds are employed in combination with the tris(3,5-di-t-butyl-4- hydroxybenzyl)isocyanurate or when the hexahydrol ,3,5-tris[B-(n-octadecylcarboxymethylthio )propionyl]-s-triazine is employed in combination with other well known and highly active stabilizers not derived from isocyanurates or 1,3,5-triazines.

Similar results are obtained when the hexahydro- 1 ,3,5-tris[B-(n-octadecylcarboxymethylthio )propionyl]-s-triazine is incorporated in high density polyethylene. Synergism was obtained in polyethylene both in combination with tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate and also with similarly substituted 1,3,5-triazines, such as hexahydro-l ,3,5-tris[B-(3,5-dit-butyl-4-hydroxyphenyl)propionyl]-s-triazine. Polyethylene stabilized in this manner had remarkable stability upon oven aging and outdoor exposure.

EXAMPLE IV Polypropylene was stabilized with 0.25 part hexahydro-l ,3 ,5-tris[/3-(n-octadecyl-2-carboxyethylthio)propionyl]-s-triazine as prepared in Example 11. Excellent polymer stability was observed when, additionally, 0.1 part tris( 3 ,5-di-t-butyl-4-hydroxybenzyl)isocyanurate was combined therewith. In this latter instance the samples subjected to 140C. oven-aging withstood 2,424 hours before failure. This is again a substantial improvement over compositions tested under identical conditions but stabilized with ,B-dilaurylthiodipropionate or a phenolic stabilizer not derived from an Additionally, or 1,3,5-triazine. Additionaly, when the above synergistic combination was employed to stabilize poly(4-methyl-pentene-l) and an ethylene-propylene copolymer similar synergistic activity was observed.

EXAMPLE V Employing a procedure similar to that described in Example, I, methylene bisacrylamide was reacted with n-octadecylthio acetate to obtain N,N'- methylenebis[B-(n-octadecylcarboxymethylthio)propionamide] which was incorporated in polypropylene, by itself, and in combination with tris(3,5-di-t-butyl-4- hydroxybenzyl)isocyanurate and hexahydro-1,3,5-' tris[B-(3,5-di-t-butyl-4-hydroxybenzyl)propionyl]-striazine and hexahydro-l,3,5-tris[B-(3,5-di-t-butyl-4- hydroxyphenyl)a-methylpropionyl]-s-triazine at 0.1 and 0.25 part levels. The components comprising the synergistic combinations were employed at a 1:1 weight ratio. Excellent stabilities were observed in all instances. The polypropylene stabilized in this manner exhibited superior resistance to outdoor aging as measured by color development of the samples.

In addition to the stabilizer systems employed above N,N'-methylenebis[/3-(n-dodecyl-2-carboxyethylthio)- propionamide[ and hexahydro-l ,3,5-tris[B-(n-dodecyl- 2-carboxyethylthio)a-methylpropionyl]-s-triazine were employed to stablize polypropylene in combination with tris( 3 ,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, tris(3-methyl-4-hydroxybenzyl) isocyanurate, hexahydrol ,3 ,S-tris[B-( 3,5-di-t-butyl-4-hydroxyphenyl )propionyl]-s-triazine and other 1,3,5-triazines substituted with various hindered phenolic groupings. The stabilization of the polypropylene was, in all instances, markedly improved over that of unstabilized polypropylene wherein R is selected from hydrogen or a methyl group, R is an alkyl radical containing from 12 to 20 carbon atoms and (b) a hydroxyphenylalkyleneyl isocyanurate of the formula I I cH, N-o-0H0H2s cm)1 2000112 wherein R is a tertiary alkyl group containing from 4 to 8 carbon atoms and R is hydrogen or an alkyl group containing 1 to 18 carbon atoms; the weight ratio of (a) to (b) ranging between about 5:1 and about 1:5.

2. The composition of claim 1 wherein the polyolefin is polypropylene, R and R of (b) are di-tertiary butyl groups and R is ortho to the hydroxy group and the stabilizer system is employed in an amount between about 0.1 percent and 2 percent weight of the total composition with the weight ratio of (a) to (b) of about 1:1.

3. A compostion of claim 1 wherein the propionamide is N,N-methylenebis[B-(n-octadecylcarboxymethylthio )propionamide].

4. A composition of claim 1 wherein the propionamide is I N,N'-methylenebis[B-(n-dodecyl-Z- carboxyethylthio )propionamide].

5. A composition of claim 3 wherein (b) is tris(3,5- di-t-butyl-4-hydroxybenzyl) isocyanurate.

6. A composition of claim 4 wherein (b) is tris(3,5-

di-t-butyl-4-hydroxylbenzyl) isocyanurate.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,76 L, 580 Dated October 9, 1973 lnv flg) Warren L. Beears It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 5, line 19, after the number 3", insert -t-- ----5 line L5, "structuarlly should read --structurally- In Column 6, line 5, "hi" should read ---di---.

In Column 9, lines 11-12, "Additionally" should read -is0cyanurate--Y-5 line 12, "Additionaly" should read ---Additionall ---3 line 37, delete the [f after propionamide.

In Claim 2, line 3 arteflz percent, add the wordv --by---.

I Signed and-' sea1ed this 24th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JRL C. MARSHALL DANN Attesting Officer Commissionerof Patents FORM PC2-1 (10-69) I e u'scoMM-oc dean-Poo a 1.1.5 GOVERNMENT PRINTING OFFICE: I!" 0-36-"4 v 

2. The composition of claim 1 wherein the polyolefin is polypropylene, R4 and R5 of (b) are di-tertiary butyl groups and R5 is ortho to the hydroxy group and the stabilizer system is employed in an amount between about 0.1 percent and 2 percent weight of the total composition with the weight ratio of (a) to (b) of about 1:1.
 3. A compostion of claim 1 wherein the propionamide is N,N''-methylenebis( Beta -(n-octadecyl-carboxymethylthio)propionamide) .
 4. A composition of claim 1 wherein the propionamide is N,N''-methylenebis( Beta -(n-dodecyl-2-carboxyethylthio)propionamide).
 5. A composition of claim 3 wherein (b) is tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate.
 6. A composition of claim 4 wherein (b) is tris(3,5-di-t-butyl-4-hydroxylbenzyl) isocyanurate. 